Prevalence of facial canal dehiscence and other bone defects by computed tomography.

Introduction: The facial nerve is the most vulnerable structure during otological surgeries. Facial canal dehiscence (FCD) is the main risk factor for iatrogenic injuries. Its prevalence in clinical studies ranges between 6 and 33.3%, while anatomical studies report 25-57%. The objective was to determine the prevalence of FCD stratified by age and gender in a healthy population.

Materials And Methods: Temporal bones from high-resolution computed tomography (CT) were analyzed. Patients with a history of trauma or tumors of the temporal bone, cholesteatomas, chronic middle ear disease, and any pathology that could modify the bone's anatomy, were excluded.

Results: A total of 184 temporal bones were included. FCD was observed in 94 (51.2%) of the analyzed bones. The tympanic portion was the most frequently affected site with 91 (49.5%), followed by the mastoid segment with 3 (1.6%). No dehiscence was found in the labyrinth portion. We observed 30 (31.9%) of the FCD involved the oval window. Other bone defects identified with the FCD included: 11 (11.7%) with a lateral semicircular canal fistula and 7 (7.4%) with tegmen tympani erosions.

Conclusion: FCD has a high prevalence among healthy patients. A pre-surgical otological evaluation using high-resolution CT should be indicated to properly assess the patient and reduce the risk of injury.